I didn't manually move the partitions. I did have Flopswap on prior to installing ED, and swap was on the SD card. ED installation then first reported an invalid argument to swapoff (I think the argument was /dev/mmcblk0p3). Then, while the ED image file was decompressing, I did a cat /proc/swaps and saw that both the N900 and the SD card were used for swapping (the N900's swap had 0 bytes used, though). Not that this explains everything...When I installed ED before (circa a year ago), I was not swapping to SD card, and subsequent Flopswap and swapping to SD card worked fine (I'd write 94% fresh swap in just a few hours or so).

I also did cat /proc/diskstats now. Looking at Flopswap's swapused.sh, it seems that swapused.sh calculates the fresh swap correctly (and I don't see any errors in the script) - the problem is that the number of written blocks (in diskstats, the 7th argument after the device name) is too low, generally 10000-30000, and rising very slowly (so it takes hours just to get to 5% fresh swap); meanwhile Conky reports hundreds of MB of swap written.

So what could be happening to my /proc/diskstats, and how could ED cause it? Obviously this doesn't look like a Flopswap issue (anymore), but if I moved this to the ED thread I might come across as a cross-poster.